Studies of the acquisitio of ASL by deaf children who do not receive input in the language until age 5 o later have demonstrated that many aspects of language are significantly affected by this delay in input. On the other hand, deaf children exposed to ASL from birth by their deaf signing parents acquire the language in much the same way that hearing children acquire their native languages. It is not clear whether the difference between native and non-native learners would remain if initial exposure were delayed less dramatically. Is there a complete correlation between age of exposure and fluency, or is there a significant period during which native-like language acquisition can be achieved? Some indication that deaf children of hearing parents can catch up with deaf children of deaf parents comes from the current study, which has found that DCHP whose exposure to ASL began by age 2 perform very similarly to DCDP on several different tests. The proposed project will continue the investigation of the effects of early exposure to ASL by moving to a longitudinal study of younger children, ages 18 to 24 months. It will examine the emergence of language, and the course of its development, in deaf children exposed from birth to native input vs. deaf children exposed early (but not at birth) to non-native input. To put these findings in context, it will be necessary to compare the acquisition of ASL with the acquisition of other languages. Thus, the proposed project will compare the acquisition of ASL by DCDP and DCHP with the acquisition by hearing children of three spoken languages: English, Japanese, and Spanish (languages which each displays certain grammatical characteristics in common with ASL). This cross-linguistic study of early syntax will provide a wealth of information on the acquisition of ASL, and on language acquisition more generally.